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Sökning: db:Swepub > Tidskriftsartikel > McKenna P. > Robson L.

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  • Clarke, R. J., et al. (författare)
  • Detection of short lived radioisotopes as a fast diagnostic for intense laser-solid interactions
  • 2006
  • Ingår i: Applied Physics Letters. - American Institute of Physics. - 0003-6951. ; 89:14
  • Tidskriftsartikel (refereegranskat)abstract
    • As a diagnostic of high-intensity laser interactions (> 10(19) W cm(-2)), the detection of radioactive isotopes is regularly used for the characterization of proton, neutron, ion, and photon beams. This involves sample removal from the interaction chamber and time consuming post shot analysis using NaI coincidence counting or Ge detectors. This letter describes the use of in situ detectors to measure laser-driven (p,n) reactions in Al-27 as an almost real-time diagnostic for proton acceleration. The produced Si-27 isotope decays with a 4.16 s half-life by the predominantly beta+ emission, producing a strong 511 keV annihilation peak. (c) 2006 American Institute of Physics.
  • McKenna, P., et al. (författare)
  • Lateral electron transport in high-intensity laser-irradiated foils diagnosed by ion emission
  • 2007
  • Ingår i: Physical Review Letters. - American Physical Society. - 1079-7114. ; 98:14
  • Tidskriftsartikel (refereegranskat)abstract
    • An experimental investigation of lateral electron transport in thin metallic foil targets irradiated by ultraintense (>= 10(19) W/cm(2)) laser pulses is reported. Two-dimensional spatially resolved ion emission measurements are used to quantify electric-field generation resulting from electron transport. The measurement of large electric fields (similar to 0.1 TV/m) millimeters from the laser focus reveals that lateral energy transport continues long after the laser pulse has decayed. Numerical simulations confirm a very strong enhancement of electron density and electric field at the edges of the target.
  • McKenna, P, et al. (författare)
  • Low- and medium-mass ion acceleration driven by petawatt laser plasma interactions
  • 2007
  • Ingår i: Plasma Physics and Controlled Fusion. - IOP Publishing. - 0741-3335. ; 49:B223, s. 223-231
  • Tidskriftsartikel (refereegranskat)abstract
    • An experimental investigation of low- and medium-mass ion acceleration from resistively heated thin foil targets, irradiated by picosecond laser pulses at intensities up to 5 × 10^20 Wcm−2, is reported. It is found that the spectral distributions of ions, up to multi-MeV/nucleon energies, accelerated from the rear surface of the target are broadly consistent with previously reported measurements made at intensities up to 5 × 10^19 Wcm−2. Properties of the backward-directed beams of ions accelerated from the target front surface are also measured, and it is found that, compared with the rear surface, higher ion numbers and charges, and similar ion energies are produced. Additionally, the scaling of the maximum ion energy as a function of ion charge and laser intensity are measured and compared with the predictions of a numerical model.
  • Robson, L, et al. (författare)
  • Scaling of proton acceleration driven by petawatt-laser-plasma interactions
  • 2007
  • Ingår i: Nature Physics. - Nature Publishing Group. - 1745-2473. ; 3:58, s. 58-62
  • Tidskriftsartikel (refereegranskat)abstract
    • The possibility of using high-power lasers to generate high-quality beams of energetic ions is attracting large global interest. The prospect of using laser-accelerated protons in medicine attracts particular interest, as these schemes may lead to compact and relatively low-cost sources. Among the challenges remaining before these sources can be used in medicine is to increase the numbers and energies of the ions accelerated. Here, we extend the energy and intensity range over which proton scaling is experimentally investigated, up to 400 J and 6×10^20 Wcm−2 respectively, and find a slower proton scaling than previously predicted. With the aid of plasma-expansion simulation tools, our results suggest the importance of time-dependent andmultidimensional effects in predicting the maximum proton energy in this ultrahigh-intensity regime. The implications of our new understanding of proton scaling for potential medical applications are discussed.
  • Robson, L, et al. (författare)
  • Volumetric intensity dependence on the formation of molecular and atomic ions within a high intensity laser focus
  • 2005
  • Ingår i: Journal of the American Society for Mass Spectrometry. - Elsevier. - 1879-1123. ; 16:1, s. 82-89
  • Tidskriftsartikel (refereegranskat)abstract
    • The mechanism of atomic and molecular ionization in intense, ultra-short laser fields is a subject which continues to receive considerable attention. An inherent difficulty with techniques involving the tight focus of a laser beam is the continuous distribution of intensities contained within the focus, which can vary over several orders of magnitude. The present study adopts time of flight mass spectrometry coupled with a high intensity (8 X 10(15) Wcm(-2)), ultra-short (20 fs) pulse laser in order to investigate the ionization and dissociation of the aromatic molecule benzene-d1 (C6H5D) as a function of intensity within a focused laser beam, by scanning the laser focus in the direction of propagation, while detecting ions produced only in a "thin" slice (400 and 800 mum) of the focus. The resultant TOF mass spectra varies significantly, highlighting the dependence on the range of specific intensities accessed and their volumetric weightings on the ionization/dissociation pathways accessed.
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